Group III nitride semiconductor light-emitting device

ABSTRACT

A Group III nitride semiconductor light-emitting device, includes a groove having a depth extending from the top surface of a p-type layer to an n-type layer is provided in a region overlapping (in plan view) with the wiring portion of an n-electrode or the wiring portion of a p-electrode. An insulating film is provided so as to continuously cover the side surfaces and bottom surface of the groove, the p-type layer, and an ITO electrode. The insulating film incorporates therein reflective films in regions directly below the n-electrode and the p-electrode (on the side of a sapphire substrate). The reflective films in regions directly below the wiring portion of the n-electrode and the wiring portion of the p-electrode are located at a level lower than that of a light-emitting layer. The n-electrode and the p-electrode are covered with an additional insulating film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a face-up-type Group III nitridesemiconductor light-emitting device whose light extraction performanceis improved by providing a reflective film in an insulating film.

2. Background Art

Patent documents 1 and 2 disclose a flip-chip-type Group III nitridesemiconductor light-emitting device in which a reflective film isprovided in an insulating film. In such a light-emitting device,migration of a metal forming the reflective film is prevented throughelectrical insulation of the film by enclosing the film with theinsulating film.

-   Patent Document 1: Japanese Patent Application Laid-Open (kokai) No.    H11-340514-   Patent Document 2: Japanese Patent Application Laid-Open (kokai) No.    2005-302747

The Group III nitride semiconductor light-emitting device having astructure disclosed in Patent Document 1 or 2 is of a flip-chip type.Conceivably, application of such a structure to a face-up-type devicecould improve the light extraction performance of the device.Specifically, the light extraction performance could be improved byproviding a structure in which a reflective film enclosed with aninsulating film is formed below an n-electrode and a p-electrode (i.e.,on the side of a sapphire substrate), so that light emitted toward then-electrode and the p-electrode is reflected by the reflective film, tothereby inhibit absorption of light by the n-electrode and thep-electrode.

The present inventors have conducted studies on a face-up-type Group IIInitride semiconductor light-emitting device having the aforementionedstructure. However, the present inventors have found that thelight-emitting device exhibits insufficiently improved light extractionperformance, since light reflected by the reflective film is absorbed bya light-emitting layer, or light reflected by a resin for sealing thedevice is absorbed by a wiring portion of the n-electrode or thep-electrode.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present invention is toprovide a face-up-type Group III nitride semiconductor light-emittingdevice whose light extraction performance is improved by providing areflective film enclosed with an insulating film below an n-electrodeand a p-electrode.

In a first aspect of the present invention, there is provided aface-up-type Group III nitride semiconductor light-emitting devicecomprising a growth substrate; an n-type layer; a light-emitting layer;a p-type layer; an n-electrode having a bonding portion and a wiringportion; a p-electrode having a bonding portion and a wiring portion; afirst insulating film; and a second insulating film,

the n-type layer, the light-emitting layer, and the p-type layer beingsequentially stacked on the growth substrate, the n-electrode and thep-electrode being formed on the first insulating film, and a portion ofeach of the n-electrode and the p-electrode other than the bondingportion being covered with the second insulating film, wherein:

the light-emitting device has a reflective film incorporated in thefirst insulating film in a region directly below each of the n-electrodeand the p-electrode, the reflective film being formed of a materialexhibiting a reflectance for light of emission wavelength higher thanthat of the wiring portion;

a groove having a depth extending from the top surface of the p-typelayer to the n-type layer is formed in at least one of a region directlybelow the wiring portion of the n-electrode and a region directly belowthe wiring portion of the p-electrode; and

the reflective film in a region directly below the region in which thegroove is formed is located at a level lower than that of thelight-emitting layer.

In a second aspect of the present invention, there is provided aface-up-type Group III nitride semiconductor light-emitting devicecomprising a growth substrate; an n-type layer; a light-emitting layer;a p-type layer; an n-electrode having a bonding portion and a wiringportion; a electrode having a bonding portion and a wiring portion; afirst insulating film; and a second insulating film,

the n-type layer, the light-emitting layer, and the p-type layer beingsequentially stacked on the growth substrate, the n-electrode and thep-electrode being formed on the first insulating film, and a portion ofeach of the n-electrode and the p-electrode other than the bondingportion being covered with the second insulating film, wherein:

the light-emitting device has a reflective film incorporated into thesecond insulating film in a region directly above each of the wiringportions of the n-electrode and the p-electrode, the reflective filmbeing formed of a material exhibiting a reflectance for light ofemission wavelength higher than that of the wiring portion;

a groove having a depth extending from the top surface of the p-typelayer to the n-type layer is formed in at least one of a region directlybelow the wiring portion of the n-electrode and a region directly belowthe wiring portion of the p-electrode; and

the reflective film in a region directly above the region in which thegroove is formed is located at a level lower than that of thelight-emitting layer.

In a third aspect of the present invention, there is provided aface-up-type Group III nitride semiconductor light-emitting devicecomprising a growth substrate; an n-type layer; a light-emitting layer;a p-type layer; an n-electrode having a bonding portion and a wiringportion; a p-electrode having a bonding portion and a wiring portion; afirst insulating film; and a second insulating film,

the n-type layer, the light-emitting layer, and the p-type layer beingsequentially stacked on the growth substrate, the n-electrode and thep-electrode being formed on the first insulating film, and a portion ofeach of the n-electrode and the p-electrode other than the bondingportion being covered with the second insulating film, wherein:

the light-emitting device has a reflective film incorporated into thefirst insulating film in a region directly below each of the n-electrodeand the p-electrode, the reflective film being formed of a materialexhibiting a reflectance for light of emission wavelength higher thanthat of the wiring portion;

the light-emitting device has a reflective film incorporated into thesecond insulating film in a region directly above each of the wiringportions of the n-electrode and the p-electrode, the reflective filmbeing formed of a material exhibiting a reflectance for light ofemission wavelength higher than that of the wiring portion;

a groove having a depth extending from the top surface of the p-typelayer to the n-type layer is formed in at least one of a region directlybelow the wiring portion of the n-electrode and a region directly belowthe wiring portion of the p-electrode; and

the reflective films in regions directly above and below the region inwhich the groove is formed are located at a level lower than that of thelight-emitting layer.

In a fourth aspect of the present invention, there is provided aface-up-type Group III nitride semiconductor light-emitting devicecomprising a growth substrate; an n-type layer; a light-emitting layer;a p-type layer; an n-electrode having a bonding portion and a wiringportion; a p-electrode having a bonding portion and a wiring portion;and a first insulating film,

the n-type layer, the light-emitting layer, and the p-type layer beingsequentially stacked on the growth substrate, and the n-electrode andthe p-electrode being formed on the first insulating film, wherein:

a groove having a depth extending from the top surface of the p-typelayer to the n-type layer is formed in at least one of a region directlybelow the wiring portion of the n-electrode and a region directly belowthe wiring portion of the p-electrode;

the wiring portion in the region in which the groove is formed islocated at a level lower than that of the light-emitting layer; and

each of the n-electrode and the p-electrode is formed of Ag, Al, an Agalloy, or an Al alloy.

In the first to fourth aspects, the term “below” refers to the casewhere a region is located more proximal to the growth substrate, and theterm “above” refers to the case where a region is located more distal inrelation to the growth substrate.

The reflective film may be a single-layer film or a multi-layer film. Inorder to improve adhesion of the reflective film to the insulating film,a film formed of, for example, Ti may be provided between the insulatingfilm and the reflective film. The material of the reflective film maybe, for example, Al, Ag, an Al alloy, an Ag alloy, or a dielectricmulti-layer film.

The wiring portion of the n-electrode may be connected to the n-typelayer by the mediation of an intermediate electrode provided on then-type layer. The wiring portion of the p-electrode may be connected toan ITO electrode on the p-type layer by the mediation of an intermediateelectrode provided on the ITO electrode.

The groove may also be provided in a region directly below the bondingportion of the n-electrode or the bonding portion of the p-electrode.However, in such a case, difficulty may be encountered in bonding a wireto the bonding portion of the n-electrode or the bonding portion of thep-electrode.

The reflective film in a region directly below the wiring portion of then-electrode or the wiring portion of the p-electrode may be provideddirectly on the n-type layer or the p-type layer.

In the first or third aspect of the invention, the reflective filmlocated directly below the wiring portion may be provided directly on aportion of the n-type layer exposed through the bottom of the groove.

In any of the first to third aspects of the invention, the reflectivefilm may be is formed of Ag, Al, an Ag alloy, an Al alloy, or adielectric multi-layer film.

In any of the first to fourth aspects of the invention, the groove maybe provided in a region directly below the wiring portion of then-electrode.

In any of the first to fourth aspects of the invention, the groove maybe is provided directly below each of the wiring portions of then-electrode and the p-electrode.

According to the present invention, there is reduced absorption of lightreflected by the reflective film by the wiring portion of then-electrode or the p-electrode or the light-emitting layer. Also, lightpropagating in a plane parallel to the main surface of the device isreadily extracted from side surfaces of the groove. Therefore, lightextraction performance is improved.

As described in the aspect, the reflective film may be formed of Ag, Al,an Ag alloy, an Al alloy, or a dielectric multi-layer film.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features, and many of the attendant advantages ofthe present invention will be readily appreciated as the same becomesbetter understood with reference to the following detailed descriptionof the preferred embodiments when considered in connection with theaccompanying drawings, in which:

FIG. 1 is a cross-sectional view of the configuration of a Group IIInitride semiconductor light-emitting device according to Embodiment 1;

FIG. 2 is a top plan view of the Group III nitride semiconductorlight-emitting device according to Embodiment 1;

FIGS. 3A to 3F are sketches showing processes for producing the GroupIII nitride semiconductor light-emitting device according to Embodiment1;

FIG. 4 is a cross-sectional view of the configuration of a Group IIInitride semiconductor light-emitting device according to Embodiment 2;

FIG. 5 is a cross-sectional view of the configuration of a Group IIInitride semiconductor light-emitting device according to Embodiment 3;

FIG. 6 is a cross-sectional view of the configuration of a Group IIInitride semiconductor light-emitting device according to Embodiment 4;

FIG. 7 is a cross-sectional view of the configuration of a Group IIInitride semiconductor light-emitting device according to anotherembodiment;

FIG. 8 is a cross-sectional view of the configuration of a Group IIInitride semiconductor light-emitting device according to Embodiment 5;

FIG. 9 is a cross-sectional view of the configuration of a Group IIInitride semiconductor light-emitting device according to anotherembodiment;

FIG. 10 is a cross-sectional view of the configuration of a Group IIInitride semiconductor light-emitting device according to still anotherembodiment;

FIG. 11 is a cross-sectional view of the configuration of a Group IIInitride semiconductor light-emitting device according to yet anotherembodiment;

FIG. 12 is a cross-sectional view of the configuration of a Group IIInitride semiconductor light-emitting device according to yet anotherembodiment; and

FIG. 13 is a cross-sectional view of the configuration of a Group IIInitride semiconductor light-emitting device according to yet anotherembodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Specific embodiments of the present invention will next be describedwith reference to the drawings. However, the present invention is notlimited to the embodiments.

Embodiment 1

FIG. 1 shows the configuration of a face-up-type Group III nitridesemiconductor light-emitting device according to Embodiment 1. FIG. 2 isa top view of the Group III nitride semiconductor light-emitting deviceaccording to Embodiment 1. FIG. 1 corresponds to a cross section takenalong line A-A of FIG. 2.

As shown in FIG. 2, the Group III nitride semiconductor light-emittingdevice according to Embodiment 1 has a rectangular shape in plan view,and includes an n-electrode 17 and a p-electrode 18. The n-electrode 17has a bonding portion 17A, and a wiring portion 17B continuous with thebonding portion 17A. Also, the p-electrode 18 has a bonding portion 18Aand a wiring portion 18B. The bonding portion 17A or 18A is a region towhich a bonding wire is connected, and voltage is applied to then-electrode 17 or the p-electrode 18 by means of the bonding wire. Thewiring portion 17B or 18B has a linear structure extending in adirection parallel to the main surface of the device, which improvescurrent diffusion in a direction parallel to the main surface of thedevice.

As shown in FIG. 1, the Group III nitride semiconductor light-emittingdevice according to Embodiment 1 includes a sapphire substrate 10; andan n-type layer 11, a light-emitting layer 12, and a p-type layer 13,which are sequentially stacked on the sapphire substrate 10, and each ofwhich is formed of a Group III nitride semiconductor. Each of the n-typelayer 11, the light-emitting layer 12, and the p-type layer 13 may haveany of conventionally known structures. For example, the n-type layer 11has a structure in which an n-contact layer, an ESD layer, and ann-cladding layer are sequentially stacked on the sapphire substrate 10.For example, the light-emitting layer 12 has an MQW structure in whichInGaN well layers and GaN barrier layers are alternately stacked. Forexample, the p-type layer 13 has a structure in which a p-cladding layerdoped and a p-contact layer are sequentially stacked on thelight-emitting layer 12. An ITO electrode 15 is formed on a specificregion of the p-type layer 13. The ITO electrode 15 may be replaced withan electrode formed of any material exhibiting permeability for light ofemission wavelength of the Group III nitride semiconductorlight-emitting device; for example, an electrode formed of anelectrically conductive transparent oxide such as ICO (indium ceriumoxide) or IZO (indium zinc oxide), or a metal thin film such as Au thinfilm. In a region overlapping (in plan view) with the wiring portion 17Bof the n-electrode 17 or the wiring portion 18B of the p-electrode 18,there are provided grooves 14 having a depth extending from the topsurface (i.e., the surface on the side opposite the sapphire substrate10) of the p-type layer 13 to the n-type layer 11 (to the n-contactlayer in the case where the n-type layer 11 is formed of a plurality oflayers). A plurality of n-side intermediate electrodes 24 are providedin specific regions at the bottoms of the grooves 14, and a plurality ofp-side intermediate electrodes 25 are provided in specific regions onthe ITO electrode 15. Each of the n-side intermediate electrodes 24 andthe p-side intermediate electrodes 25 has, for example, a structure ofNi/Au/Al (i.e., a structure in which an Ni film, an Au film, and an Alfilm are sequentially stacked on the sapphire substrate 10) wherein thesymbol “/” refers to a layered structure; for example, “A/B” refers to alayered structure in which layer B is formed after formation of layer A(the same shall apply hereinafter).

A SiO₂ insulating film 16 (corresponding to the first insulating film ofthe present invention) is provided so as to continuously cover the sidesurfaces and bottom surface of the grooves 14, the p-type layer 13, andthe ITO electrode 15. The insulating film 16 may be formed of, in placeof SiO₂, an insulating material exhibiting permeability for light ofemission wavelength of the Group III nitride semiconductorlight-emitting device, such as Si₃N₄, Al₂O₃, or TiO₂. The insulatingfilm 16 includes therein reflective films 19 which are formed in regionsdirectly below the n-electrode 17 and the p-electrode 18 (the term“below” refers to the case where a region is located on the side of thesapphire substrate 10 (the same shall apply hereinafter), and the term“above” refers to the case where a region is located on the sideopposite the sapphire substrate 10). The reflective films 19 areenclosed with the insulating film 16 and thus are electricallyinsulated, whereby metal migration is prevented. Since the grooves 14are provided, the reflective films 19 in regions directly below thewiring portion 17B of the n-electrode 17 and the wiring portion 18B ofthe p-electrode 18 are located at a level lower than that of thelight-emitting layer 12. Meanwhile, the reflective films 19 in regionsdirectly below the bonding portion 17A of the n-electrode 17 and thebonding portion 18A of the p-electrode 18 are located at a level higherthan that of the p-type layer 13 (the term “above” refers to the casewhere a region is located more distal from the sapphire substrate 10;the same shall apply hereinafter).

Each of the reflective films 19 is formed of a material exhibiting areflectance higher than that of the n-electrode 17 or the p-electrode18, such as Al, Ag, an Al alloy, or an Ag alloy. The reflective film 19may be a single-layer film or a multi-layer film. When the reflectivefilm 19 is a multi-layer film, the film may be formed of, for example,Al alloy/Ti, Ag alloy/Al, Ag alloy/Ti, Al/Ag/Al, or Ag alloy/Ni. Inorder to improve adhesion of the reflective film 19 to the insulatingfilm 16, a thin film formed of, for example, Ti, Cr, or Al may beprovided between the reflective film 19 and the insulating film 16. Thereflective film 19 may be formed of a dielectric multi-layer film. Thedielectric multi-layer film is a multi-layer film formed of a pluralityof alternately stacked pairs of films, each pair including a film formedof a material of low refractive index and a film formed of a material ofhigh refractive index, wherein the thickness d of each film is adjustedso as to satisfy the relation d=λ/(4×n) (λ: wavelength of interest(emission wavelength of the Group III nitride semiconductorlight-emitting device according to Embodiment 1), n: refractive index ofthe film). The material of low refractive index may be, for example,SiO₂ (refractive index: about 1.46) or MgF₂ (refractive index: about1.38), and the material of high refractive index may be, for example,SiN (refractive index: about 2.0), TiO₂ (refractive index: about 2.3),ZrO₂ (refractive index: about 2.05), or Ta₂O₅ (refractive index: about2.16). From the viewpoint of improvement of the reflectance of thedielectric multi-layer film, preferably, a large difference inrefractive index is provided between the material of low refractiveindex and the material of high refractive index. The dielectricmulti-layer film is preferably formed of a large number of pairs offilms. The number of pairs of films is preferably 9 or more. However,when the dielectric multi-layer film is formed of a very large number ofpairs of films, the overall thickness of the dielectric multi-layer filmincreases, and problems may arise in production processes. Therefore,the number of pairs of films is preferably 30 or less. Specific examplesof the dielectric multi-layer film include a multi-layer film formed ofalternately stacked 12 pairs of films, each pair including an SiO₂ filmhaving a thickness of 78 nm and an SiN film having a thickness of 56 nm,and a multi-layer film formed of alternately stacked 12 pairs of films,each pair including an SiO₂ film having a thickness of 78 nm and an TiO₂film having a thickness of 45 nm.

On the insulating film 16 are formed the n-electrode 17 having thebonding portion 17A and the wiring portion 17B, and the p-electrode 18having the bonding portion 18A and the wiring portion 18B. Each of then-electrode 17 and the p-electrode 18 is formed of, for example,Ti/Ni/Au/Al. Since the grooves 14 are provided, the wiring portion 17Band the wiring portion 18B are located at a level lower than that of thelight-emitting layer 12. Meanwhile, the bonding portion 17A and thebonding portion 18A are located directly above the p-type layer 13 bythe mediation of the insulating film 16. The insulating film 16 hasholes 20 and 21 for exposing the n-side intermediate electrodes 24 andthe p-side intermediate electrodes 25. The wiring portion 17B of then-electrode 17 is connected to the n-side intermediate electrodes 24 viathe holes 20, and the wiring portion 18B of the p-electrode 18 isconnected to the p-side intermediate electrodes 25 via the holes 21. Then-side intermediate electrodes 24 are provided for the purpose ofimproving contact between the n-type layer 11 and the n-electrode 17,and the p-side intermediate electrodes 25 are provided for the purposeof improving contact between the ITO electrode 15 and the p-electrode18.

The n-electrode 17 and the p-electrode 18 (excluding the bondingportions 17A and 18A) are covered with an SiO₂ insulating film 22(corresponding to the second insulating film of the present invention).The insulating film 22 may be formed of, in place of SiO₂, an insulatingmaterial exhibiting transparency for light of emission wavelength of theGroup III nitride semiconductor light-emitting device, such as Si₂N₄,Al₂O₃, or TiO₂. The insulating film 22 includes therein reflective films23 in regions directly above the wiring portion 17B and the wiringportion 18B. Similar to the case of the reflective films 19, thereflective films 23 are enclosed with the insulating film 22 and thusare electrically insulated, whereby metal migration is prevented. Sincethe grooves 14 are provided, the reflective films 23 are located at alevel lower than that of the light-emitting layer 12.

Each of the reflective films 23 is formed of a material exhibiting areflectance higher than that of the n-electrode 17 or the p-electrode18, such as Al, Ag, an Al alloy, or an Ag alloy. The material of thereflective film 23 may be identical to or different from that of thereflective film 19. The reflective film 23 may be a single-layer film ora multi-layer film. When the reflective film 23 is a multi-layer film,the film may be formed of, for example, Al alloy/Ti, Ag alloy/Al, Agalloy/Ti, Al/Ag/Al, or Ag alloy/Ni. In order to improve adhesion of thereflective film 23 to the insulating film 22, a thin film formed of, forexample, Ti, Cr, or Al may be provided between the reflective film 23and the insulating film 22. Similar to the case of the reflective film19, the reflective film 23 may be formed of a dielectric multi-layerfilm.

As shown in plan view in FIG. 2, shaded portions correspond to regionsin which the reflective films 19 and 23 are formed. Shaded portions 30(diagonally right-down shaded portions) correspond to regions in whichonly the reflective films 19 are provided in plan view, and which arelocated directly below the bonding portion 17A of the n-electrode 17 andthe bonding portion 18A of the p-electrode 18 (the term “below” refersto the case where a region is located more proximal to the sapphiresubstrate 10; the same shall apply hereinafter). Shaded portions 40(diagonally right-up shaded portions) correspond to regions in which thereflective films 19 overlap with the reflective films 23 in plan view.The reflective films 19 are located in regions directly below the wiringportion 17B of the n-electrode 17 and the wiring portion 18B of thep-electrode 18, and the reflective films 23 are located in regionsdirectly above the wiring portion 17B and the wiring portion 18B.

The Group III nitride semiconductor light-emitting device according toEmbodiment 1 is of a face-up type, in which light is extracted from thetop side of the device (i.e., the side of the n-electrode 17 and thep-electrode 18). Since the reflective films 19 enclosed with theinsulating film 16 and the reflective films 23 enclosed with theinsulating film 22 are provided directly below the n-electrode 17 andthe p-electrode 18, absorption of light by the n-electrode 17 and thep-electrode 18 is inhibited, whereby light extraction performance isimproved. In the device, the reflective films 19 in regions directlybelow the wiring portion 17B of the n-electrode 17 and the wiringportion 18B of the p-electrode 18, as well as the reflective films 23 inregions directly above the wiring portion 17B and the wiring portion 18Bare located at a level lower than that of the light-emitting layer 12.Therefore, light reflected by the reflective films 19 and 23 is lesslikely to be directed toward the light-emitting layer 12, and absorptionof light by the light-emitting layer 12 is suppressed. Meanwhile, lighttransmitted from the side below the wiring portions 17B and 18B isreflected by the difference in refractive index between the insulatingfilm 16 and the n-type layer 11, and absorption of light by the wiringportions 17B and 18B is suppressed. When the device is sealed with asealing resin, light which is reflected by the sealing resin and returnsto the wiring portion 17B of the n-electrode 17 and the wiring portion18B of the p-electrode 18 is reflected by the reflective films 23, andthus absorption of light by the wiring portions 17B and 18B isprevented. Also, light propagating in a direction parallel to the mainsurface of the device (i.e., plane parallel to the main surface of thesapphire substrate 10) is readily extracted from the side surfaces ofthe grooves 14 to the outside of the device. For these reasons, theGroup III nitride semiconductor light-emitting device according toEmbodiment 1 exhibits improved light extraction performance.

Next will be described processes for producing the Group III nitridesemiconductor light-emitting device according to Embodiment 1.

Firstly, an n-type layer 11, a light-emitting layer 12, and a p-typelayer 13 are sequentially formed on a sapphire substrate 10 by MOCVD.The raw material gases, etc. employed for MOCVD are as follows: TMG(trimethylgallium) as a Ga source, TMI (trimethylindium) as an Insource, TMA (trimethylaluminum) as an Al source, ammonia as a nitrogensource, silane as an n-type doping gas, cyclopentadienylmagnesium as ap-type doping gas, and hydrogen or nitrogen as a carrier gas. Then, ITOelectrodes 15 (thickness: 100 nm) are formed by vapor deposition onregions of the p-type layer 13 (FIG. 3A).

Subsequently, specific portions of the p-type layer 13 are subjected todry etching, to thereby form grooves 14 so that the n-type layer 11 isexposed through the bottoms of the grooves 14 (FIG. 3B). The grooves 14are formed by etching to have such a depth that reflective films 19 and23 which will be formed later are located at a level lower than that ofthe light-emitting layer 12 (on the side of the sapphire substrate 10).

Then, p-side intermediate electrodes 25 and n-side intermediateelectrodes 24 are formed, by vapor deposition and the lift-off process,on specific regions of the ITO electrodes 15 and on specific regions ofthe n-type layer 11 exposed through the groove bottoms, respectively,followed by washing and thermal treatment at 570° C. (FIG. 3C). Then-side intermediate electrode 24 and the p-side intermediate electrode25 may be separately formed from different materials. However, when then-side intermediate electrode 24 and the p-side intermediate electrode25 are formed from the same material, these electrodes can be formedsimultaneously. Therefore, production processes can be simplified, andproduction cost can be reduced.

Next, a first insulating film 16 a (thickness: 100 nm) is formed on theentire top surface of the resultant product by CVD. Then, reflectivefilms 19 are formed on specific regions (corresponding to regionsdirectly below an n-electrode 17 and a p-electrode 18 which will beformed later) of the first insulating film 16 a by vapor deposition andthe lift-off process. The reflective films 19 may be formed by, in placeof the lift-off process, patterning (e.g., etching). Since the depth ofthe grooves 14 is designed as described in the process of FIG. 3B, thereflective films 19 in regions directly below the wiring portion 17B ofthe n-electrode 17 and the wiring portion 18B of the p-electrode 18 arelocated at a level lower than that of the light-emitting layer 12 (onthe side of the sapphire substrate 10). Meanwhile, the reflective films19 in regions directly below the bonding portion 17A of the n-electrode17 and the bonding portion 18A of the p-electrode 18 are located at alevel higher than that of the p-type layer 13. Then, second insulatingfilms 16 b (thickness: 100 nm) are formed on the first insulating film16 a and on the reflective films 19 by CVD. The first insulating film 16a and the second insulating films 16 b together form an insulating film16, to thereby form a structure in which the reflective films 19 areenclosed with the insulating film 16 (FIG. 3D).

Subsequently, portions of the insulating film 16 corresponding to thetops of the n-side intermediate electrodes 24 and the p-sideintermediate electrodes 25 are subjected to dry etching, to thereby formholes 20 and 21 so that the n-side intermediate electrodes 24 and thep-side intermediate electrodes 25 are exposed through the bottoms of theholes 20 and 21. Then, the n-electrode 17 and the p-electrode 18 areformed on regions of the insulating film 16 corresponding to thereflective films 19 by vapor deposition and the lift-off process (FIG.3E). Thus, the n-side intermediate electrodes 24 are connected to thewiring portion 17B of the n-electrode 17 via the holes 20, and thep-side intermediate electrodes 25 are connected to the wiring portion18B of the p-electrode 18 via the holes 21. Since the depth of thegrooves 14 is designed as described in the process of FIG. 3B, thewiring portion 17B of the n-electrode 17 and the wiring portion 18B ofthe p-electrode 18 are located at a level lower than that of thelight-emitting layer 12. The bonding portion 17A of the n-electrode 17and the bonding portion 18A of the p-electrode 18 are located, by themediation of the insulating film 16, above the reflective films 19provided above the p-type layer 13.

Next, an insulating film 22 (thickness: 100 nm) is formed on the entiretop surface of the resultant product by CVD. Then, reflective films 23are formed on specific regions (corresponding to regions directly abovethe wiring portion 17B of the n-electrode 17 and the wiring portion 18Bof the p-electrode 18) of the insulating film 22 by vapor deposition andthe lift-off process (FIG. 3F). The reflective films 23 may be formedby, in place of the lift-off process, patterning (e.g., etching). Sincethe depth of the grooves 14 is designed as described in the process ofFIG. 3B, the reflective films 23 are located at a level lower than thatof the light-emitting layer 12.

Thereafter, an insulating film 22 is again formed on the entire topsurface of the resultant product, to thereby enclose the reflectivefilms 23 with the insulating film 22. Then, holes are formed, by dryetching, in a region of the insulating film directly above the bondingportion 17A of the n-electrode 17 and in a region of the insulating filmdirectly above the bonding portion 18A of the p-electrode 18, so thatthe bonding portion 17A and the bonding portion 18A are exposed throughthe bottoms of the holes. Thus, the Group III nitride semiconductorlight-emitting device according to Embodiment 1, which is shown in FIGS.1 and 2, is produced.

Embodiment 2

FIG. 4 is a cross-sectional view of the configuration of a face-up-typeGroup III nitride semiconductor light-emitting device according toEmbodiment 2. The Group III nitride semiconductor light-emitting deviceaccording to Embodiment 2 has the same configuration as the Group IIInitride semiconductor light-emitting device according to Embodiment 1,except that the reflective films 19 are replaced with reflective films119 which are provided directly on the n-type layer 11 and on the p-typelayer 13 (without the mediation of the insulating film 16). Similar tothe case of the reflective films 19, the reflective films 119 areprovided directly below the wiring portion 17B of the n-electrode 17 andthe wiring portion 18B of the p-electrode 18 by the mediation of theinsulating film 16, and are located at a level lower than that of thelight-emitting layer 12.

Similar to the case of Embodiment 1, the Group III nitride semiconductorlight-emitting device according to Embodiment 2 exhibits improved lightextraction performance. The reasons for this are as follows. Thereflective films 119 in regions directly below the wiring portion 17B ofthe n-electrode 17 and the wiring portion 18B of the p-electrode 18, aswell as the reflective films 23 in regions directly above the wiringportion 17B and the wiring portion 18B are located at a level lower thanthat of the light-emitting layer 12. Therefore, light reflected by thereflective films 119 and 23 is less likely to be directed toward thelight-emitting layer 12, and absorption of light by the light-emittinglayer 12 is suppressed. When the device is sealed with a sealing resin,light which is reflected by the sealing resin and returns to the wiringportion 17B of the n-electrode 17 and the wiring portion 18B of thep-electrode 18 is reflected by the reflective films 23, and thusabsorption of light by the wiring portions 17B and 18B is prevented.Also, light propagating in a direction parallel to the main surface ofthe device (i.e., plane parallel to the main surface of the sapphiresubstrate 10) is readily extracted from the side surfaces of the grooves14 to the outside of the device.

For production of the Group III nitride semiconductor light-emittingdevice according to Embodiment 2, the process for forming the firstinsulating film 16 a—which is required for production of the Group IIInitride semiconductor light-emitting device according to Embodiment1—can be omitted. Therefore, in the case of Embodiment 2, productionprocesses can be further simplified.

In Embodiment 2, the reflective films 119 are provided directly on then-type layer 11 and the p-type layer 13. Therefore, the reflective films119 are preferably formed of a material which does not come into ohmiccontact with the n-type layer 11 or the p-type layer 13; for example, Alor an Al alloy. Each of the reflective films 119 may be a single-layerfilm or a multi-layer film.

Embodiment 3

FIG. 5 is a cross-sectional view of the configuration of a face-up-typeGroup III nitride semiconductor light-emitting device according toEmbodiment 3. The Group III nitride semiconductor light-emitting deviceaccording to Embodiment 3 has the same configuration as the Group IIInitride semiconductor light-emitting device according to Embodiment 1,except that the reflective films 19 are omitted.

Similar to the case of Embodiment 1, the Group III nitride semiconductorlight-emitting device according to Embodiment 3 exhibits improved lightextraction performance. The reasons for this are as follows. Thereflective films 23 in regions directly above the wiring portion 17B ofthe n-electrode 17 and the wiring portion 18B of the p-electrode 18 arelocated at a level lower than that of the light-emitting layer 12.Therefore, light reflected by the reflective films 23 is less likely tobe directed toward the light-emitting layer 12, and absorption of lightby the light-emitting layer 12 is suppressed. When the device is sealedwith a sealing resin, light which is reflected by the sealing resin andreturns to the wiring portion 17B of the n-electrode 17 and the wiringportion 18B of the p-electrode 18 is reflected by the reflective films23, and thus absorption of light by the wiring portions 17B and 18B isprevented. Also, light propagating in a direction parallel to the mainsurface of the device (i.e., plane parallel to the main surface of thesapphire substrate 10) is readily extracted from the side surfaces ofthe grooves 14 to the outside of the device.

For production of the Group III nitride semiconductor light-emittingdevice according to Embodiment 3, the process for forming the reflectivefilms 19 can be omitted. Therefore, production processes can besimplified, as compared with the case of the Group III nitridesemiconductor light-emitting device according to Embodiment 1.

Embodiment 4

FIG. 6 is a cross-sectional view of the configuration of a face-up-typeGroup III nitride semiconductor light-emitting device according toEmbodiment 4. The Group III nitride semiconductor light-emitting deviceaccording to Embodiment 4 has the same configuration as the Group IIInitride semiconductor light-emitting device according to Embodiment 1,except that the reflective films 23 are omitted.

The Group III nitride semiconductor light-emitting device according toEmbodiment 4 exhibits improved light extraction performance for thereasons described below. The reflective films 19 in regions directlybelow the wiring portion 17B of the n-electrode 17 and the wiringportion 18B of the p-electrode 18 are located at a level lower than thatof the light-emitting layer 12. Therefore, light reflected by thereflective films 19 is less likely to be directed toward thelight-emitting layer 12, and absorption of light by the light-emittinglayer 12 is suppressed. Also, light propagating in a direction parallelto the main surface of the device (i.e., plane parallel to the mainsurface of the sapphire substrate 10) is readily extracted from the sidesurfaces of the grooves 14 to the outside of the device. For thesereasons, the Group III nitride semiconductor light-emitting deviceaccording to Embodiment 4 exhibits improved light extractionperformance.

For production of the Group III nitride semiconductor light-emittingdevice according to Embodiment 4, the process for forming the reflectivefilms 23 can be omitted. Therefore, production processes can besimplified, as compared with the case of the Group III nitridesemiconductor light-emitting device according to Embodiment 1.

Embodiment 5

FIG. 8 is a cross-sectional view of the configuration of a face-up-typeGroup III nitride semiconductor light-emitting device according toEmbodiment 5. The Group III nitride semiconductor light-emitting deviceaccording to Embodiment 5 has the same configuration as the Group IIInitride semiconductor light-emitting device according to Embodiment 1,except that the reflective films 19 and 23 are omitted, and then-electrode 17 and the p-electrode 18 are respectively replaced with ann-electrode 117 and a p-electrode 118, each of which is formed of anelectrically conductive material of high reflectance as in the case ofthe reflective film 19 or 23. Although the materials of the n-electrode117 and the p-electrode 118 are different from those of the n-electrode17 and the p-electrode 18, respectively, the n-electrode 117 and thep-electrode 118 have the same structures as the n-electrode 17 and thep-electrode 18, respectively. Specifically, the n-electrode 117 has abonding portion 117A and a wiring portion 117B, and the p-electrode 118has a bonding portion 118A and a wiring portion 118B. The electricallyconductive material of high reflectance exhibits high reflectance forlight of emission wavelength of the Group III nitride semiconductorlight-emitting device. The electrically conductive material of highreflectance may be a single-layer material formed of Ag, Al, an Agalloy, an Al alloy, or the like, or a multi-layer material containingsuch a single-layer material; for example, Al alloy/Ti/Au/Al, Agalloy/Al, Ag alloy/Ti/Au/Al, Al/Ag/Al, or Ag alloy/Ni/Ti/Au/Al.

As shown in FIG. 9, a metal layer 80 formed of, for example, Au, Ti/Au,or Ni/Ti/Au may be stacked on the bonding portion 117A of then-electrode 117 or the bonding portion 118A of the p-electrode 118, soas to further improve contact between the bonding portion 117A or 118Aand a bonding wire. As shown in FIG. 10, the wiring portion 117B of then-electrode 117 and the wiring portion 118B of the p-electrode 118 maybe exposed without formation of the insulating film 22 on the wiringportions 117B and 118B. In such a case, when each of the n-electrode 117and the p-electrode 118 has a multi-layer structure, the outermost layer(i.e., the layer most distal from the sapphire substrate 10) is notnecessarily an Al layer. For example, the n-electrode 117 or thep-electrode 118, which is generally formed of Al alloy/Ti/Au/Al or Agalloy/Ti/Au/Al, may be formed of Al alloy/Ti/Au, Ag alloy/Ti/Au, or Agalloy/Ni/Ti/Au, with the outermost Al layer being omitted.

In the Group III nitride semiconductor light-emitting device accordingto Embodiment 5, since each of the n-electrode 17 and the p-electrode 18itself is formed of a material of high reflectance, absorption of lightby the n-electrode 17 and the p-electrode 18 is inhibited, and lightextraction performance is improved. In the Group III nitridesemiconductor light-emitting device according to Embodiment 5, since thegrooves 14 are provided, the wiring portion 17B of the n-electrode 17and the wiring portion 18B of the p-electrode 18 are located at a levellower than that of the light-emitting layer 12. Similar to the case ofthe reflective films 19 and 23 in Embodiment 1, the wiring portions 17Band 18B are formed of a material of high reflectance. Therefore, lightreflected by the wiring portions 17B and 18B is less likely to bedirected toward the light-emitting layer 12, and absorption of light bythe light-emitting layer 12 is suppressed. When the device is sealedwith a sealing resin, light which is reflected by the sealing resin andreturns to the n-electrode 17 and the p-electrode 18 is reflected by then-electrode 17 and the p-electrode 18 (i.e., absorption of light bythese electrodes is prevented). Also, light propagating in a directionparallel to the main surface of the device (i.e., plane parallel to themain surface of the sapphire substrate 10) is readily extracted from theside surfaces of the grooves 14 to the outside of the device. For thesereasons, the Group III nitride semiconductor light-emitting deviceaccording to Embodiment 5 exhibits improved light extractionperformance.

For production of the Group III nitride semiconductor light-emittingdevice according to Embodiment 5, the process for forming the reflectivefilms 19 and 23 can be omitted. Therefore, production processes can besimplified and production cost can be reduced, as compared with the caseof the Group III nitride semiconductor light-emitting device accordingto Embodiment 1.

In each of Embodiments 1 to 5, by means of the n-side intermediateelectrodes 24 and the p-side intermediate electrodes 25, the n-typelayer 11 is indirectly connected to the wiring portion 17B of then-electrode 17, and the ITO electrodes 15 are indirectly connected tothe wiring portion 18B of the p-electrode 18. However, the n-sideintermediate electrodes 24 and the p-side intermediate electrodes 25 maybe omitted; the wiring portion 17B of the n-electrode 17 may be directlyconnected to the n-type layer 11; and the wiring portion 18B of thep-electrode 18 may be directly connected to the ITO electrodes 15. FIG.11 is a cross-sectional view of the configuration of a modification ofthe Group III nitride semiconductor light-emitting device according toEmbodiment 1, in which the n-side intermediate electrodes 24 and thep-side intermediate electrodes 25 are omitted; the wiring portion 17B ofthe n-electrode 17 is directly connected to the n-type layer 11; and thewiring portion 18B of the p-electrode 18 is directly connected to theITO electrodes 15.

In Embodiments 1 to 5, the grooves 14 are provided in regions directlybelow the wiring portion 17B of the n-electrode 17 and the wiringportion 18B of the p-electrode 18, such that the reflective films 19 and23 in the regions are located at a level lower than that of thelight-emitting layer 12. The groove 14 may be provided in a regiondirectly below one or both of the bonding portion 17A of the n-electrode17 and the bonding portion 18A of the p-electrode 18. However, in such acase, difficulty may be encountered in attaching a bonding wire, sincethe bonding portion 17A and/or the bonding portion 18A is located at alower level. FIG. 12 is a cross-sectional view of the configuration of amodification of the Group III nitride semiconductor light-emittingdevice according to Embodiment 1, in which the groove 14 is alsoprovided in a region directly below the bonding portion 17A of then-electrode 17. As is clear from FIG. 12, through provision of theadditional groove 14, the bonding portion 17A of the n-electrode 17 islocated at a level lower than that of the bonding portion 17A of then-electrode 17 of the Group III nitride semiconductor light-emittingdevice according to Embodiment 1 shown in FIG. 1.

In Embodiments 1 to 5, the groove 14 may be provided only in a regiondirectly below the wiring portion 17B of the n-electrode 17 (i.e., thegroove 14 is not provided in a region directly below the wiring portion18B of the p-electrode 18). In such a case, since the area of thelight-emitting layer 12 increases as compared with the cases ofEmbodiments 1 to 5, emission performance may be improved. FIG. 7 is across-sectional view of the configuration of a modification of the GroupIII nitride semiconductor light-emitting device according to Embodiment1, in which the groove 14 is provided only in a region directly belowthe wiring portion 17B of the n-electrode 17 (i.e., the groove 14 is notprovided in a region directly below the wiring portion 18B of thep-electrode 18). FIG. 13 is a cross-sectional view of the configurationof a modification of the Group III nitride semiconductor light-emittingdevice according to Embodiment 5, in which the groove 14 is providedonly in a region directly below the wiring portion 17B of then-electrode 17 (i.e., the groove 14 is not provided in a region directlybelow the wiring portion 18B of the p-electrode 18).

In contrast, the groove 14 may be provided only in a region directlybelow the wiring portion 18B of the p-electrode 18 (i.e., the groove 14is not provided in a region directly below the wiring portion 17B of then-electrode 17). Similar to the aforementioned case, since the area ofthe light-emitting layer 12 increases as compared with the cases ofEmbodiments 1 to 5, emission performance may be improved.

The Group III nitride semiconductor light-emitting device of the presentinvention can be employed as a light source of an illumination apparatusor a display apparatus.

What is claimed is:
 1. A face-up-type Group III nitride semiconductorlight-emitting device, comprising: a growth substrate; an n-type layer;a light-emitting layer; a p-type layer; an n-electrode including abonding portion and a wiring portion; a p-electrode including a bondingportion and a wiring portion; a first insulating film; and a secondinsulating film, the n-type layer, the light-emitting layer, and thep-type layer being sequentially stacked on the growth substrate, then-electrode and the p-electrode being formed on the first insulatingfilm, and a portion of each of the n-electrode and the p-electrode otherthan the bonding portion being covered with the second insulating film,wherein the light-emitting device includes a reflective filmincorporated in the first insulating film in a region directly beloweach of the n-electrode and the p-electrode, the reflective filmcomprising a material exhibiting a reflectance for light of emissionwavelength higher than that of the wiring portion, wherein a groovehaving a depth extending from a top surface of the p-type layer to then-type layer is formed in at least one of a region directly below thewiring portion of the n-electrode and a region directly below the wiringportion of the p-electrode, and wherein the reflective film which isformed in the groove is located at a level lower than that of thelight-emitting layer.
 2. A face-up-type Group III nitride semiconductorlight-emitting device, comprising: a growth substrate; an n-type layer;a light-emitting layer; a p-type layer; an n-electrode including abonding portion and a wiring portion; a p-electrode including a bondingportion and a wiring portion; a first insulating film; and a secondinsulating film, the n-type layer, the light-emitting layer, and thep-type layer being sequentially stacked on the growth substrate, then-electrode and the p-electrode being formed on the first insulatingfilm, and a portion of each of the n-electrode and the p-electrode otherthan the bonding portion being covered with the second insulating film,wherein the light-emitting device includes a reflective filmincorporated in the second insulating film in a region directly aboveeach of the wiring portions of the n-electrode and the p-electrode, thereflective film comprising a material exhibiting a reflectance for lightof emission wavelength higher than that of the wiring portion, wherein agroove having a depth extending from a top surface of the p-type layerto the n-type layer is formed in at least one of a region directly belowthe wiring portion of the n-electrode and a region directly below thewiring portion of the p-electrode, and wherein the reflective film whichis formed in the groove is located at a level lower than that of thelight-emitting layer.
 3. A face-up-type Group III nitride semiconductorlight-emitting device, comprising: a growth substrate; an n-type layer;a light-emitting layer; a p-type layer; an n-electrode including abonding portion and a wiring portion; a p-electrode including a bondingportion and a wiring portion; a first insulating film; and a secondinsulating film, the n-type layer, the light-emitting layer, and thep-type layer being sequentially stacked on the growth substrate, then-electrode and the p-electrode being formed on the first insulatingfilm, and a portion of each of the n-electrode and the p-electrode otherthan the bonding portion being covered with the second insulating film,wherein the light-emitting device includes a first reflective filmincorporated in the first insulating film in a region directly beloweach of the n-electrode and the p-electrode, the first reflective filmcomprising a material exhibiting a reflectance for light of emissionwavelength higher than that of the wiring portion, wherein thelight-emitting device further comprises a second reflective filmincorporated in the second insulating film in a region directly aboveeach of the wiring portions of the n-electrode and the p-electrode, thesecond reflective film comprising a material exhibiting a reflectancefor light of emission wavelength higher than that of the wiring portion,wherein a groove having a depth extending from a top surface of thep-type layer to the n-type layer is formed in at least one of a regiondirectly below the wiring portion of the n-electrode and a regiondirectly below the wiring portion of the p-electrode, and wherein thefirst and second reflective films which are formed in the groove arelocated at a level lower than that of the light-emitting layer.
 4. AGroup III nitride semiconductor light-emitting device according to claim1, wherein the reflective film comprises Ag, Al, an Ag alloy, an Alalloy, or a dielectric multi-layer film.
 5. A Group III nitridesemiconductor light-emitting device according to claim 2, wherein thereflective film comprises Ag, Al, an Ag alloy, an Al alloy, or adielectric multi-layer film.
 6. A Group III nitride semiconductorlight-emitting device according to claim 3, wherein the first reflectivefilm comprises Ag, Al, an Ag alloy, an Al alloy, or a dielectricmulti-layer film, and wherein the second reflective film comprises Ag,Al, an Ag alloy, an Al alloy, or a dielectric multi-layer film.
 7. AGroup III nitride semiconductor light-emitting device according to claim1, wherein the groove is provided in a region directly below the wiringportion of the n-electrode.
 8. A Group III nitride semiconductorlight-emitting device according to claim 2, wherein the groove isprovided in a region directly below the wiring portion of then-electrode.
 9. A Group III nitride semiconductor light-emitting deviceaccording to claim 3, wherein the groove is provided in a regiondirectly below the wiring portion of the n-electrode.
 10. A Group IIInitride semiconductor light-emitting device according to claim 1,wherein the groove is provided directly below each of the wiringportions of the n-electrode and the p-electrode.
 11. A Group III nitridesemiconductor light-emitting device according to claim 2, wherein thegroove is provided directly below each of the wiring portions of then-electrode and the p-electrode.
 12. A Group III nitride semiconductorlight-emitting device according to claim 3, wherein the groove isprovided directly below each of the wiring portions of the n-electrodeand the p-electrode.
 13. A Group III nitride semiconductorlight-emitting device according to claim 1, wherein a back surface ofthe reflective film is contacted directly to a surface of the n-typelayer exposed through a bottom of the groove, and a top surface of thereflective film is covered with the first insulating film.
 14. A GroupIII nitride semiconductor light-emitting device according to claim 3,wherein a back surface of the first reflective film is contacteddirectly to a surface of the n-type layer exposed through a bottom ofthe groove, and a top surface of the first reflective film is coveredwith the first insulating film.
 15. A Group III nitride semiconductorlight-emitting device according to claim 7, wherein a back surface ofthe reflective film is contacted directly to a surface of the n-typelayer exposed through a bottom of the groove, and a top surface of thereflective film is covered with the first insulating film.
 16. A GroupIII nitride semiconductor light-emitting device according to claim 9,wherein a back surface of the first reflective film is contacteddirectly to a surface of the n-type layer exposed through a bottom ofthe groove, and a top surface of the first reflective film is coveredwith the first insulating film.
 17. A Group III nitride semiconductorlight-emitting device according to claim 4, wherein a back surface ofthe reflective film is contacted directly to a surface of the n-typelayer exposed through a bottom of the groove, and a top surface of thereflective film is covered with the first insulating film.
 18. A GroupIII nitride semiconductor light-emitting device according to claim 6,wherein a back surface of the first reflective film is contacteddirectly to a surface of the n-type layer exposed through a bottom ofthe groove, and a top surface of the first reflective film is coveredwith the first insulating film.